The best interest of the child: McEwan's novel and the questions it raises

Family Court judge Fiona (Maye) heads off by cab to a South London hospital to visit with the 17-year-old Jehovah's Witness boy who's dying of leukemia and declines blood transfusion on religious grounds; he's a bit sassy, precocious, and polymathic, like so many Brits (in literature, anyway) and probably in some ways like the polymath author of this novel (The Children Act - I know, another awful title), Ian McEwan, who absorbs (and regurgitates?) a tremendous amount of knowledge and info in this and other novels: in this, he's become authoritative on the, esp. family law, on architecture, on music, so far. In any event, she, and we, are impressed by the boy and saddened by him, too, his desperate need to keep talking with Fiona, to entertain her; oddly, he plays a little tune he's learned on the violin, and she knows it a setting for a Yeats poem, "I was young and foolish" (the opposite, btw, of My Back Pages, the great Dylan [not Thomas] lyric) and she sings it to his accompaniment. Oh those polymath Brits! Perhaps we're meant to see that she is that much more cultured than his rather poky parents who are insisting he not have the transfusion and who, as Fiona writes in her ruling, have kept him too sheltered for him to truly make up his own mind. The decision she writes is the one that most readers would wish for - save this poor f-ing kid's life and order the transfusion - but her reasoning is rather weird and narcissistic: we know far more about life than this teenager, and if he could ever break free from the cultish religion of his parents he, too, would choose life. This ruling does not seem to be w/in the scope of the law, which is to allow people to make their own decision as long as those decisions are reasoned and not harmful to others - though perhaps it is within the spirit of the eponymous act, which puts the best interest of children paramount. Had he been of age, i.e., 18, this would not have been at issue, but at 17 his views should not be relevant and she should simply rule against the parents without regard to the boy's own pleadings. At end of this section (3), Fiona's husband returns home w/ suitcase and, figuratively, hat in hand, and says he could not bring himself to carry on, or even begin, the longed-for affair with the 20-something. Do we believe him? What damage has this done to their marriage - or has his wished for infidelity exposed fissures in the marriage that neither had recognized?